Consumers are asking more questions about products they are using in and around the house, and they want to know the facts concerning pressure treated wood. The following questions are some of the most commonly asked by consumers. Dealing with these questions openly will dispel any misconceptions potential users may have about pressure treated wood.

Q. Why build with wood?

Wood is our only renewable natural resource and provides thousands of products to improve our lives. ; Wood’s advantages to the construction industry are many. It can be worked and fabricated on the job; it is strong; has a great insulation value and can be finished in a variety of ways; it has warmth and an eye-appealing tone. It has limitless possibilities for creative design inspirations, and is the most economical building material from the standpoint of both material and labor.  Wood creates a congenial atmosphere in which to live and work.

Q. Why use preservatives?

Wood preservatives extend the useful life of wood products by penetrating and remaining in the wood, thereby neutralizing it as a food supply for decay fungi and wood destroying insects

Q. What is pressure treatment?

Pressure treatment is a process that forces chemical preservatives into the wood. Wood is placed inside a closed cylinder, then vacuum and pressure are applied to force the preservatives into the wood cells in a pressurized cylinder. The preservatives help protect the wood from attack by termites and fungal decay.

Q. How do wood preservatives work?

A wood preservative must have the ability to do three things: (1) penetrate the wood, (2) neutralize the food supply within wood in which decay fungi and wood destroying insects live, and (3) be present in sufficient quantities in a non-leachable form so that its protection outlasts the useful life of the wood product. Effective preservatives will also kill existing decay, fungi and insects, which might already exist in the wood. A true wood preservative is a toxic material, to be used with care. It will penetrate wood fibers and stop the organic enemies of wood.

Q. Where should pressure treated wood be used?

Treated wood can be used for wood structures that require resistance to termites and fungal decay – in decks, fences, gazebos, playground equipment, docks, marinas, raised garden beds, landscape, agricultural uses and industrial applications, such as utility poles, railway ties and bridges.  A water repellent or wood sealer specially formulated for pressure treated lumber may be applied periodically to reduce cracking and splitting of wood and thus the likelihood of children getting splinters.

Q. For what projects should I not use preserved wood?

Do not use preserved wood for the following:

  • Preserved wood should not be used where it may come into direct or indirect contact with drinking water, except for uses involving incidental contact such as fresh water docks and bridges.
  • Do not use preserved wood under circumstances where the preservative may become a component of food, animal feed or beehives.
  • Do not use preserved wood as mulch.

Q. Is there any material that I can’t use with preserved wood?

Do not use preserved wood in direct contact with aluminum; when using preserved wood in close proximity to aluminum products, such as aluminum siding, flashing, and door and window frames, a 1/4″ minimum space must be allowed for between the preserved wood and the aluminum products. Polyethylene or nylon spacers can be used to maintain the 1/4″ spacing. Another option is to use a polyethylene barrier, with a minimum thickness of 10 mils, between the preserved wood and the aluminum product to prevent direct contact of the wood and the aluminum.

Q. Can pressure treated wood be used indoors?

Treated wood may be used indoors for applications where protection against termites and fungal decay is needed.  Pressure treated wood should not be used, or where it would otherwise come in contact with drinking water or food, such as countertops or cutting boards.  The Canadian Food Inspection Agency (CFIA) does not recommend any wood for use as a cutting surface since food particles are likely to be embedded in its porous surface.  This can encourage bacterial growth, creating any unsanitary environment.


Q. Does working with treated wood require special safety precautions?

The use and handling guidelines for treated wood reflect common sense and good safety practices for handling any wood.  Inhalation of sawdust can cause nose and throat irritation, and protecting eyes from any foreign matter is advisable.  Wearing gloves provides extra protection against splinters, and good personal hygiene should be practiced in the shop and on the job.  Hands should be washed after handling any type of wood or after doing any type of construction work.

Q. Is there a preferred way to store preserved wood while working on my projects?

There are a few simple precautions you should take to store your preserved wood:

  • Unload lumber in a dry place
  • Elevate lumber on stringers to prevent absorption of ground moisture and to allow air circulation. Do not store lumber in direct contact with the ground.
  • Cover lumber stored in an open area with a material that will give protection from the elements, but be porous enough to allow moisture to escape. Polyethylene or similar non-porous covers may trap moisture.

Q. Why do I need to use an end-cut preservative?

When building your outdoor project with preserved wood, it is important to protect the cut ends of boards from fungal decay. All cuts and holes that expose untreated wood should be liberally brush-coated with two applications of an end-cut preservative (copper naphthenate in ground contact or zinc naphthenate above ground) before the wood is installed. Always follow the manufacturer’s recommendations.

Q. How should I dispose of pressure treated wood?

Do not burn treated wood. If burned, toxic chemicals may be produced as part of the ashes. Pressure treated wood should be disposed of by ordinary trash collection or burial. Industrial users may dispose of treated wood in commercial or industrial incinerators in accordance with provincial and federal regulations.

Q. Why can I not burn treated lumber?

Preserved wood must not be burned because combustion breaks the unique bond formed between the preservative solution and the wood. When this bond is destroyed, the components of the preservative can be released in the form of ash and particulates, which can be harmful if inhaled. It is completely proper and legal to send treated wood to a landfill.

Q. How do I clean mold from my deck?

Remove mold with soap and water. Mold growth can and does occur on the surface of many products, including untreated and treated wood, during prolonged surface exposure to excessive moisture conditions. To remove mold from the treated wood surface, wood should be allowed to dry. Typically, mild soap and water can be used to remove remaining surface mold.

Q. How do I make my deck last?

To protect your investment, a regular maintenance program is important. A good maintenance program begins during construction and continues throughout the life of a project. Here are some important construction tips:

  • Use an end-cut preservative (copper naphthenate in ground contact or zinc naphthenate above ground) on all cuts and holes that expose untreated wood.
  • Use a fastening system that provides maximum holding power and corrosion resistance, and follow the manufacturer’s recommendation for all metal products
  • Use screws to add extra holding power for decking and all applications where appearance is important.
  • Drill pilot holes, especially when working near the edge of the board. This will minimize splitting.
  • Apply a weather resistant finish. Any exposed wood, pressure treated or not, should be protected from the weather. Application of a quality clear water repellent or semi-transparent stain which contains a water repellent will help minimize the cycles of moisture take-up and loss the wood goes through outdoors. For maximum protection, a water repellent should be applied as soon as the deck or other project construction is completed.

Q. Can I apply a finish to my deck or fence?

If you desire to apply a paint, stain, clear water repellent or other finish to preserved wood, we recommend following the manufacturer’s instructions and label of the finishing product. Before you start, we recommend you apply the finishing product to a small exposed test area before finishing the entire project to ensure it provides the intended result before proceeding.


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